/*
 * Copyright (c) 2008 Open Kernel Labs, Inc. (Copyright Holder).
 * All rights reserved.
 *
 * 1. Redistribution and use of OKL4 (Software) in source and binary
 * forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 *     (a) Redistributions of source code must retain this clause 1
 *         (including paragraphs (a), (b) and (c)), clause 2 and clause 3
 *         (Licence Terms) and the above copyright notice.
 *
 *     (b) Redistributions in binary form must reproduce the above
 *         copyright notice and the Licence Terms in the documentation and/or
 *         other materials provided with the distribution.
 *
 *     (c) Redistributions in any form must be accompanied by information on
 *         how to obtain complete source code for:
 *        (i) the Software; and
 *        (ii) all accompanying software that uses (or is intended to
 *        use) the Software whether directly or indirectly.  Such source
 *        code must:
 *        (iii) either be included in the distribution or be available
 *        for no more than the cost of distribution plus a nominal fee;
 *        and
 *        (iv) be licensed by each relevant holder of copyright under
 *        either the Licence Terms (with an appropriate copyright notice)
 *        or the terms of a licence which is approved by the Open Source
 *        Initative.  For an executable file, "complete source code"
 *        means the source code for all modules it contains and includes
 *        associated build and other files reasonably required to produce
 *        the executable.
 *
 * 2. THIS SOFTWARE IS PROVIDED ``AS IS'' AND, TO THE EXTENT PERMITTED BY
 * LAW, ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED.  WHERE ANY WARRANTY IS
 * IMPLIED AND IS PREVENTED BY LAW FROM BEING DISCLAIMED THEN TO THE
 * EXTENT PERMISSIBLE BY LAW: (A) THE WARRANTY IS READ DOWN IN FAVOUR OF
 * THE COPYRIGHT HOLDER (AND, IN THE CASE OF A PARTICIPANT, THAT
 * PARTICIPANT) AND (B) ANY LIMITATIONS PERMITTED BY LAW (INCLUDING AS TO
 * THE EXTENT OF THE WARRANTY AND THE REMEDIES AVAILABLE IN THE EVENT OF
 * BREACH) ARE DEEMED PART OF THIS LICENCE IN A FORM MOST FAVOURABLE TO
 * THE COPYRIGHT HOLDER (AND, IN THE CASE OF A PARTICIPANT, THAT
 * PARTICIPANT). IN THE LICENCE TERMS, "PARTICIPANT" INCLUDES EVERY
 * PERSON WHO HAS CONTRIBUTED TO THE SOFTWARE OR WHO HAS BEEN INVOLVED IN
 * THE DISTRIBUTION OR DISSEMINATION OF THE SOFTWARE.
 *
 * 3. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR ANY OTHER PARTICIPANT BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*
 * Description:   ARM user memory access functions
 */

#ifndef __ARCH__ARM__USER_ACCESS_H__
#define __ARCH__ARM__USER_ACCESS_H__

#if defined(__GNUC__)

INLINE word_t user_read_word(word_t *ptr)
{
    word_t res;
    /*
     * Load word from user memory. Note that %0 must be different from
     * %1, or the processor will produce unpredictable results. We force
     * this using by placing 'res' as an early-clobber register.
     */
    __asm__ __volatile__ (
        "   ldrt    %0,     [%1]        \n"
        : "=&r" (res)
        : "r" (ptr)
        : "memory", "r0", "r1"
    );
    return res;
}

INLINE void user_write_word(word_t *ptr, word_t value)
{
    __asm__ __volatile__ (
        "   strt    %0,     [%1]        \n"
        :: "r" (value), "r" (ptr)
        : "memory"
    );
}

#else /* !__GNUC__ */

/*
 * We only use inline assembly for GNU g++. The RVCT compiler introduces some
 * 'interesting' problems, and has an implementation in "user_access.spp".
 */

extern "C" {
    word_t user_read_word(word_t *ptr);
    void user_write_word(word_t *ptr, word_t value);
}

#endif /* !__GNUC__ */

INLINE bool
user_compare_and_set_word(word_t * ptr, word_t expect, word_t value)
{
    /* Since we don't have SMP arm processors sequential access is atomic. */
    if (user_read_word(ptr) == expect) {
        user_write_word(ptr, value);
        return true;
    }
    return false;
}


#endif /*!__ARCH__ARM__USER_ACCESS_H__*/
